Field of the Invention
The halogenation of copper phthalocyanine gives an amorphous to microcrystalline agglomerated crude polyhalocopper phthalocyanine which, because of the high degree of agglomeration is opaque and has a low color strength. For this reason, the crude pigment is converted by recrystallization into pigmentary forms having optimum color properties. This process, also referred to as conditioning or finishing, is carried out, for example, at elevated temperatures in 90-98% strength by weight sulfuric acid, in xylene (DE-B-No. 2,013,818), o-nitrophenol (DE-C-No. 1,242,180) or in a mixture of benzoic acid and/or alkylbenzoic acids and water at from 80.degree. to 130.degree. C. (DE-A No. 3,442,118).
Pigmentary forms having interesting color properties are obtained by heat treatment in o-nitrophenol. However, this conditioning medium has considerable disadvantages: it has a strong odor since it has a marked vapor pressure at as low as room temperature, it sublimes readily and it is volatile together with steam. Other disadvantages are that o-nitrophenol has a low melting point and marked solubility in water, resulting in losses during the recovery process.
A further disadvantage is that the o-nitrophenolate anion formed in the removal of the nitrophenol by the addition of an alkali metal hydroxide has a high affinity for the polyhalocopper phthalocyanine pigment, so that a long wash process is required for substantially quantitative removal of the nitrophenolate.
Finishing in xylene according to DE-B-No. 2,013,818, in which the pigmentary form is obtained directly in the form of a nonagglomerated powder by freeze-drying, must be carefully carried out and monitored to prevent supercrystallization.